Is a nib blue label worth $1650? Should I buy it or another .223?

I sure do hope so.. for I have one.. :)

if used sp1's go for a grand and more.. then, nib 762x39's (some what rare) should at least go for what you stated. You'll have to find mags for it.. and the source is USA mags. The only mags they sold that actually work.. :)

what ammo do you shoot?

That price seems to be about right, maybe a little towards the higher end for a NIB R6830.

If you're looking for one to use as a shooter, why not save yourself a few hundred and buy a used, LNIB specimen? They come up for sale in the Equipment Exchange and other online sale/auction sites fairly regularly in the $1300-$1400 range.

I have been checking in to the 7.62X39 myself and from what I have learned, (talking to both DPMS and DEL-TON) there is a feeding problem with the gun mostly due to the low quality mags you must use. I was told that the most common mags available, the 10 round MWG Plastic mags and USA mags both offer hit and miss type of reliabality.

Because of the reliability problem with them I am now thinking about getting a 300 Whisper upper, the 300 Whisper uses AR mags with total reliability.  It is built on the 221 fireball case and shoots 125 to 240 gr bullets. Cor-bon offers it and reloaders can buy brass and dies.  

www.quarterbore.com/300whisper/index.html

I would like to eventually have a .300 Whisper/Fireball upper receiver myself. The ballistics look great and you can load it with most any .30 caliber bullet. The problem is that you either have to pay Corban ammunition prices or roll your own. Neither one of these options sound attractive for the shooter who wants a cheap to feed blaster. This is where the 7.62x39 AR15 shines. I have a total of about 20 magazines for my 2 7.62x39 AR15s and they all work great. I wouldn't let the minor magazine issues scare away anyone interested in the 7.62x39 AR.